Sentence comprehension is one of our most frequent cognitive acts, yet it is not well understood. We propose to work on a number of aspects of comprehension and sentence memory. In order to study comprehension while it is happening, reaction time measures of processing complexity, especially phoneme-monitoring, are used when possible. A subsidiary aim of the project is to clarify the mechanisms involved in pheneme-monitoring itself. The first problem of comprehension is that of accessing words from the mental lexicon. We propose a network model of lexical access which can resolve some of contradictory results in the literature. Experiments on the roles of context and ambiguity are used to test the model. The second problem is that of parsing the input. A specific model of this process is described as well as experimental investigations stimulated by it. The relationship between lexical access and parsing is also studied. In addition, some related studies on lexical access and structure building in preschool children are proposed. These studies will use a new reaction time technique that we have developed for use with children. Pilot work has led us to believe that there may be important individual differences in the ways that listeners use semantic information to aid lexical access. We develop some of the implications of this and propose futher tests. Finally, we discuss network models of sentence memory and propose some cued recall tests of certain classes of memory models. Taken together, the proposed research investigates a substantial number of the sub-problems (though by no means all of them) in the area of sentence comprehension.